/RethinkDB Ruby

Storing binary objects

RethinkDB supports a native binary object type, letting you use ReQL to store binary objects directly in the database. The ReQL driver will transparently translate between the ReQL type and the Ruby String class.

Note: The binary object type is meant for data that cannot be reliably stored as UTF-8 strings, such as uploaded files. If you’re working with data that can be stored as strings, it’s usually easier to stick to the string data type.

For these examples, we’ll assume that the RethinkDB connection is available in global scope as conn.

Storing uploaded files in the database

It’s a common task for web applications to accept file uploads from users; with RethinkDB you can store these files directly in the database.

def save_file(file_path, save_name, user_id)
    # Store the file at 'file_path' with the filename 'save_name'.
    fh = File.open(file_path, 'rb')
    contents = fh.read()
        :user_id => user_id,
        :filename => save_name,
        :file => r.binary(contents)

In save_file, we pass a path to the uploaded file (which may be in a temporary storage directory, even with a temporary name depending on the uploading library we’ve used), the name to save the file with, and the id of the user who’s uploaded the file. The binary ReQL command is used to store the file’s contents as a binary object in the file field.

def get_user_file_ids(user_id)
    # Retrieve the IDs of previously-saved files for a user as an array of
    # hashes: [ { :id => x, :filename => y }, ...]
    return r.table('files').filter({ :user_id => user_id }).
        pluck('id', 'filename').run(conn)

def get_file(file_id):
    Retrieve a file by its ID. Returns a hash with 'filename' and 'file'
    return r.table('files').get(file_id).pluck('file', 'filename').run(conn)

Then, there are two functions for retrieving files: one to retrieve a directory of a user’s uploaded files (get_user_file_ids) and one to retrieve the actual file itself (get_file). We don’t have to use binary again here; the ReQL driver will return the proper data type for the file field in our object.

Here’s another, more fun example: adding Gravatar avatars to user accounts. We can use http to retrieve them.

require 'digest'

def add_gravatar(user_id):
    Add a gravatar field with the binary avatar icon to user accounts if they
    have an avatar associated with their email address.
    email = r.table('users').get(user_id)['email'].run(conn)
    hash = Digest::MD5.hexdigest email
    gravatar_url = 'http://www.gravatar.com/avatar/' + hash + '?d=retro'
        'gravatar': r.http(gravatar_url, :result_format => 'binary')

Where’s r.binary? You don’t need it in this case, because r.http will return a binary object with the :result_format => 'binary' option. (If the MIME type on the sending server is set correctly, you can even leave that off, and r.http will figure out the correct type.)

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